>But I don't actually buy the whole "better interface" argument. What are the large differences between the two? Other than a skin they seem to have mostly the same buttons along the top. The menu layout is different, but not hugely so.

I fired up Mozilla 1.7.3. I happened to have around.

First reaction: It sucks compared to FF. This is the same reaction I got to GIMP 1.x, just not as strong of course.

Second reaction: There's a bar under the URL bar which I can minimize, but not remove. I tried to find a way to remove it, but I can't. What's worse, nothing outside the URL bar reacts to right-clicking. In FF, you get to check on-off different toolbars or to open the customize menu when you right-click.

The preferences menu is A LOT less messy in FF. Same goes for menus in general.

Finally, there isn't necessarily a huge outward difference between a good and a bad interface: if the difference was obvious, we wouldn't have so many bad UIs.